Winter Warnings

As the mercury drops, runners risk hypothermia and more. Avoid the big chill.

One day last winter, the wind in Boulder, Colorado, was blowing snow sideways and the temperature hovered in the single digits. But there was no question Scott Elliott, 44, was going out. The eight-time Pikes Peak Ascent champion was midway toward his goal of running Bear Peak-a six-mile, 2,776-foot climb-100 days in a row. "The first 10 minutes suck, but after that, you're warm and cozy," he says. "You are your own furnace-as long as you don't stop, you'll stay warm."

Elliott's exploits may have been extreme, but his attitude toward the conditions wasn't. The biggest health hazards that runners face in the cold-hypothermia and frostbite--are mostly avoidable. "With the right gear and a little common sense, running in below-zero temperatures can be safe," says John Castellani, Ph.D., an exercise physiologist at the U.S. Army Research Institute of Environmental Medicine who helped write the American College of Sports Medicine's guidelines on exercising in the cold. In fact, Castellani says it's more dangerous to run when temperatures skyrocket than when they tumble-as long as you prepare.

Temperature Control

Hypothermia strikes when your body loses more heat than it can produce. Depending on the severity, hypothermia can cause mild to violent shivering, numbness, uncoordination, confusion, and, in extreme cases, death. Dampness-either from precipitation or sweat-greatly increases your risk. "Moisture lowers your body temperature substantially," Castellani says. "You're more likely to develop hypothermia at 40 degrees and damp than at 25 and dry." To stay dry, wear water- and wind-proof materials that shield you from the elements, with clothing that wicks sweat (polypropylene, not cotton) underneath. Shed your jacket once you warm up; put it back on if conditions worsen or if you need to slow down (the slower your pace, the less heat you'll generate and the colder you'll feel).

Although frostbite-the freezing of skin-can occur in temperatures below 32?F, your risk is low so long as you are covered up, dry, and moving, says Castellani. Hats and face masks are essential for protecting your face, nose, and ears. Some runners smear balms on their skin to prevent windburn. But don't let that create a false sense of security. "Skin with Vaseline on it is just as vulnerable to frostbite as skin without it," he says. Your fingers and toes are also prone to frostbite. Don't blow into your gloves for warmth: Your breath is moist, which will make your hands even colder. Keep your feet dry, too-sidestep puddles, run on plowed surfaces, and wear moisture-wicking socks. If necessary, invest in some light gaiters to keep snow out of your shoes.

While you can run safely on even the coldest days with proper clothing, there's a danger to exercising too hard when the temperature drops, says Kenneth Rundell, Ph.D., director of respiratory research and the human physiology laboratory at Marywood University in Scranton, Pennsylvania. Cold air can dry out and irritate your upper airways, which could lead to a burning sensation in the lungs or a hacking cough, Rundell says. The harder you breathe, the greater the damage. "On really cold days, you're better off doing slow, long distances than speedwork," Rundell says. If you do run fast, wear a face mask or neck gaiter over your nose and mouth to warm the air you inhale.

When you're checking the weather report, pay attention to wind chill, which increases your rate of heat loss. "When it's 30 degrees out with a 10- to 15-mile-per-hour wind, it will feel as if it's 20 degrees," says Castellani. Head into the wind at the beginning of an out-and-back run so the tailwind will warm you on your way back. If that's not possible, carry an extra layer to wear for the return trip.

Also, find a route that shelters you from blustery weather, says Amy Freeze, a marathoner and aptly named meteorologist for Fox News Chicago. "Trails in wooded areas are ideal," she says. "Cities with tall buildings don't offer the protection you might think-these streets become wind tunnels. In urban areas, run on the most exposed side of the street so the sun reaches you and keeps you warm."